We report on in situ etching of planar and masked InP wafers using phosphorous trichloride (PCl3) in a metal organic vapor phase epitaxy (MOVPE) reactor at different pressures and temperatures using a design of experiment (DOE) approach. In situ etching of a masked wafer shows an increase in etch rate between two closely spaced oxide pads and is referred to as selective area etching (SAE). InP etch rate of planar wafers increased for higher reactor temperatures and pressures over the parameter space evaluated as measured by in situ optical reflectance. InP selective area etch rate and etch rate enhancement also increased with higher reactor temperatures and pressures as measured by Dektak profilometry. Two-dimensional (2-D) modeling of SAE based on vapor phase diffusion of PCl3 shows reasonable agreement with actual measurements. From the 2-D modeling, D/k values were determined and varied from 54 to 120 mu m over the reactor parameter space examined. Highest reactor temperature and lowest reactor pressure resulted in the largest D/k value. Pre-etching masked InP wafers with PCl3 reduce the effect of excessive edge growth enhancement in subsequent selective area growth (SAG) and improves wafer planarity that is beneficial to the fabrication of integrated optoelectronic devices. (C) 2007 Elsevier B.V. All rights reserved.